Dual Air Brake System; Air Brake Operation - freightliner S2 Operator's Manual

Hydraulic and Air Brake Systems

Dual Air Brake System

A dual air brake system consists of two independent
air brake systems that use a single set of brake con-
trols. Each system has its own reservoir, plumbing,
and brake chambers. The primary air system oper-
ates the service brakes on the rear axle; the second-
ary air system operates the service brakes on the
front axle.
Primary Air Brake System
Loss of air pressure in the primary air system causes
the rear service brakes to become inoperative. The
front brakes will continue to be operated by the sec-
ondary air system.
Secondary Air Brake System
Loss of air pressure in the secondary air system
causes the front axle brakes to become inoperative.
The rear service brakes will continue to be operated
by the primary air system.
Emergency Braking System
When air pressure is lost in one air system, the air
compressor will operate, but the air supply in the
leaking system will not be replenished. There will be
enough air in the working system to stop the vehicle
safely. The dual air brake system thus provides
emergency braking capability. When the low air pres-
sure warning light and emergency buzzer first come
on, stop the vehicle immediately. Do not drive the
vehicle until the cause of the problem is corrected.
Parking Brakes
Pulling out the yellow diamond-shaped knob (parking
brake control valve) on the auxiliary dash panel ap-
plies the parking brakes (spring brakes). See
Fig. 13.1.

Air Brake Operation

WARNING
Do not operate the vehicle with the front brakes
backed off or disconnected. Backing off or dis-
connecting the front brakes will not improve ve-
hicle handling and may lead to loss of vehicle
13.1
11/21/2006
Fig. 13.1, Parking Brake Control Valve
control, resulting in property damage or personal
injury.
Before driving the vehicle, secure all loose items in
the vehicle so that they will not fly forward during a
full brake application.
Parking Brake Interlock, Optional
NOTICE
Do not continually press down on the parking
brake control valve (yellow knob) without press-
ing down on the service brake pedal. This will
damage the safety interlock.
The service brakes and parking brakes have a safety
interlock that prevents the unintentional release of
the parking brake. These instructions need to be fol-
lowed for the appropriately equipped vehicle to re-
lease the parking brake interlock.
Parking Brake Interlock Release
1. Depress the brake pedal.
2. Push the parking brake control valve in.
Parking Brake and Ignition Key Release
1. Turn the ignition key to the ON position.
2.
Depress the brake pedal.
3. Push the parking brake control valve in.
Parking Brake, Ignition Key, Wheel Chair
Lift Interlock Release
1.
Turn the ignition key to the ON position.
f430360a